1. Field of the Invention
The present invention relates generally to a process for manufacturing the metal contact of semiconductor device, and more particularly to avoid the fluorination of the metal contact.
2. Description of the Prior Art
As electrical components are made smaller, various strategies have been adopted to reduce the amount of space devoted to connections between the chip containing the integrated circuit devices and the printed circuit board on which the chips are mounted. Electrical connections between integrated circuits on a chip and the printed circuit board are made through bonding pads typically provided at the periphery of the chip. Conventional bonding pad structures may include a bonding metal layer and a barrier metal layer deposited over an underlying dielectric layer such as a silicon oxide layer. The bonding metal layer is in electrical contact with one or more semiconductor devices in the chip. The barrier metal layer on the underlying dielectric layer helps adhere the bonding metal layer, typically aluminum, to the underlying dielectric layer.
Connections between the bonding pads of a chip and the leads printed on the circuit board have conventionally been provided through the lead frame used as part of lead frame packaging methods. In such lead frame packaging methods, the chip is mounted to a frame that incorporates an array of electrical leads, with thin bonding wires connecting the bonding pads to the electrical leads on the lead frame. The entire chip and lead frame assembly is encapsulated in plastic and then mounted on the printed circuit board through the leads extending from the package. Another packaging method that is called the chip-on-board method, and the semiconductor chip is mounted directly to the printed circuit board, have significant space and weight advantages over conventional lead frame packaging methods. Electrical connections between the bonding pads of the chip and the circuit board on which the chip is mounted are typically provided by wire bonding thin wires between the chips bonding pads and the leads printed on the board. The wire bonds may be formed using a variety of techniques including ultrasonic bonding and thermocompression bonding. Ultrasonic bonding uses ultrasonic waves or vibration to attach the wire to the bonding pad. Thermocompression bonding uses a combination of elevated temperature and compressive force to attach the wire to the bonding pad. Both of these bonding techniques impart mechanical and/or thermal energy directly to the bonding pad area and so can damage the bonding pad and the chip. Furthermore, in the conventional process, the protecting layer is fluorinated to form a fluoride layer on the protecting layer after performing the plasma process with fluoride, it will result in the decrease of stress in the metal pad that will produce many defects during follow-up process. For example, it reduces electrical contact between the bonding pad and the integrated circuit devices on the chip, which decreases the reliability and reduces the life of the chip. In light of the multi-inter layers, the metal contact can be fluoridized during the process for forming the contact window or the via hole above the metal layer.
In accordance with the above description, a new and improved method for forming the metal contact of the semiconductor device is therefore necessary, so as to raise the yield and quality of the follow-up process.
In accordance with the present invention, a new method for forming the bounding pad or the metal contact is provided that substantially overcomes drawbacks of above mentioned problems arised from the conventional methods.
Accordingly, it is an object of the present invention to provide a new method for forming the metal contact of the semiconductor device, the present invention applies an ashing process with oxygen, so as to avoid fluoridizing the metal layer. Furthermore, a large fluoride content on the protecting layer can be stripped by the way of using the method in the present invention, so as to prevent the bonding pad from being fluoridized with the remained fluoride in the follow-up process. So, this invention can effectively raise the quality and the yield of the process.
In accordance with the present invention, a new method for avoiding fluoridization of metal contact in the semiconductor device is disclosed. First of all, a semiconductor substrate having a metal contact thereon is provided. Then a protecting layer is formed on the semiconductor substrate and the metal contact. Afterward, an etching process is performed to etch through the protecting layer until exposing a partial surface of the metal contact, so as to form and define a predetermined opening in the protecting layer, wherein an etching-reactive layer is formed on the protecting layer after finishing the plasma etching process. Finally, a stripping process is performed to remove the etching-reactive layer on the protecting layer and form a contact window and a metal contact thereof without fluoride, whereby it is avoided reacting the etching remainder with the metal pad during the follow-up process.